One important consideration in manufacturing pharmaceutical packages or other vessels for storing or other contact with fluids, for example vials and pre-filled syringes, is that the contents of the pharmaceutical package or other vessel desirably will have a substantial shelf life. During this shelf life, it can be important to isolate the material filling the pharmaceutical package or other vessel from the external environment as well as the vessel wall containing it, or from barrier coatings or layers or other functional layers applied to the pharmaceutical package or other vessel wall to avoid leaching material from the pharmaceutical package or other vessel wall, barrier coating or layer, or other functional layers into the prefilled contents or vice versa.
Since many of these pharmaceutical packages or other vessels are inexpensive and used in large quantities, for certain applications it will be useful to reliably obtain the necessary shelf life without increasing the manufacturing cost to a prohibitive level.
For decades, most parenteral therapeutics have been delivered to end users in Type I medical grade borosilicate glass vessels such as vials or pre-filled syringes. The relatively strong, impermeable and inert surface of borosilicate glass has performed adequately for most drug products. However, the recent advent of costly, complex and sensitive biologics as well as such advanced delivery systems as auto injectors has exposed the physical and chemical shortcomings of glass pharmaceutical packages or other vessels, including possible contamination from metals, flaking, delamination, and breakage, among other problems. Moreover, glass contains several components which can leach out during storage and cause damage to the stored material.
In more detail, borosilicate pharmaceutical packages or other vessels exhibit a number of drawbacks.
Glass is manufactured from sand containing a heterogeneous mixture of many elements (silicon, oxygen, boron, aluminum, sodium, calcium) with trace levels of other alkali and earth metals. Type I borosilicate glass consists of approximately 76% SiO2, 10.5% B2O3, 5% A12O3, 7% Na2O and 1.5% CaO and often contains trace metals such as iron, magnesium, zinc, copper and others. The heterogeneous nature of borosilicate glass creates a non-uniform surface chemistry at the molecular level. Glass forming processes used to create glass vessels expose some portions of the vessels to temperatures as great as 1200° C. Under such high temperatures alkali ions migrate to the local surface and form oxides. The presence of ions extracted from borosilicate glass devices may be involved in degradation, aggregation and denaturation of some biologics. Many proteins and other biologics must be lyophilized (freeze dried), because they are not sufficiently stable in solution in glass vials or syringes.
In glass syringes, silicone oil is typically used as a lubricant to allow the plunger tip, piston, stopper, or seal to slide in the barrel. Silicone oil has been implicated in the precipitation of protein solutions such as insulin and some other biologics. Additionally, the silicone oil coating or layer is often non-uniform, resulting in syringe failures in the market.
Glass pharmaceutical packages or other vessels are prone to breakage or degradation during manufacture, filling operations, shipping and use, which means that glass particulates may enter the drug. The presence of glass particles has led to many FDA Warning Letters and to product recalls.
Glass-forming processes do not yield the tight dimensional tolerances required for some of the newer auto-injectors and delivery systems.
As a result, some companies have turned to plastic pharmaceutical packages or other vessels, which provide tighter dimensional tolerances and less breakage than glass.
Although plastic is superior to glass with respect to breakage, dimensional tolerances and surface uniformity, its use for primary pharmaceutical packaging remains limited due to the following shortcomings:
Gas (oxygen) permeability: Plastic allows small molecule gases to permeate into (or out of) the device. The permeability of plastics to gases can be significantly greater than that of glass and, in many cases (as with oxygen-sensitive drugs such as epinephrine), plastics previously have been unacceptable for that reason.
Water vapor transmission: Plastics allow water vapor to pass through devices to a greater degree than glass. This can be detrimental to the shelf life of a solid (lyophilized) drug. Alternatively, a liquid product may lose water in an arid environment.
Leachables and extractables: Plastic pharmaceutical packages or other vessels contain organic compounds that can leach out or be extracted into the drug product. These compounds can contaminate the drug and/or negatively impact the drug's stability.
Clearly, while plastic and glass pharmaceutical packages or other vessels each offer certain advantages in pharmaceutical primary packaging, neither is optimal for all drugs, biologics or other therapeutics. Thus, there can be a desire for plastic pharmaceutical packages or other vessels, in particular plastic syringes, with gas and solute barrier properties which approach the properties of glass. Moreover, there can be a need for plastic syringes with sufficient lubricity and/or passivation or protective properties and a lubricity and/or passivation layer or pH protective coating which can be compatible with the syringe contents. There also can be a need for glass vessels with surfaces that do not tend to delaminate or dissolve or leach constituents when in contact with the vessel contents.
There are additional considerations to be taken into account when manufacturing a prefilled syringe. Prefilled syringes are commonly prepared and sold so the syringe does not need to be filled before use, and can be disposed of after use. The syringe can be prefilled with saline solution, a dye for injection, or a pharmaceutically active preparation, for some examples.
Commonly, the prefilled syringe can be capped at the distal end, as with a cap (or, if the hypodermic needle is preinstalled, a needle shield that can also be a cap), and can be closed at the proximal end by its drawn plunger tip, piston, stopper, or seal. The prefilled syringe can be wrapped in a sterile package before use. To use the prefilled syringe, the packaging and cap are removed, optionally a hypodermic needle or another delivery conduit can be attached to the distal end of the barrel, the delivery conduit or syringe can be moved to a use position (such as by inserting the hypodermic needle into a patient's blood vessel or into apparatus to be rinsed with the contents of the syringe), and the plunger tip, piston, stopper, or seal can be advanced in the barrel to inject the contents of the barrel.
An important consideration regarding medical syringes can be to ensure that the plunger tip, piston, stopper, or seal can move at a constant speed and with a constant force when it is pressed into the barrel. A similar consideration applies to vessels such as pharmaceutical vials which have to be closed by a stopper, and to the stopper itself, and more generally to any surface which is to provide smooth operation of moving parts and/or be passivated or protectively coated.
A non-exhaustive list of documents of possible relevance includes U.S. Pat. Nos. 5,824,198; 5,616,369; 5,468,520; and 5,364,666; and European Patent 0 375 778 B1. These documents are all incorporated by reference.